FrostCal

When to Plant Onions in New Hampshire

In a typical New Hampshire location, start seeds indoors Feb 22 – Mar 8, then transplant outdoors Apr 5 – Apr 19. Across the state, the outdoor planting window starts as early as Mar 24 in Salem and as late as Apr 16 in Berlin.

Method Start indoors, then transplant
Days to maturity 90–120 days

Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Onions Planting Dates by City

CityStart indoorsTransplant
ManchesterFeb 19 – Mar 5Apr 2 – Apr 16
NashuaFeb 19 – Mar 5Apr 2 – Apr 16
ConcordFeb 27 – Mar 13Apr 10 – Apr 24
East ConcordFeb 27 – Mar 13Apr 10 – Apr 24
Derry VillageFeb 19 – Mar 5Apr 2 – Apr 16
DoverFeb 22 – Mar 8Apr 5 – Apr 19
RochesterFeb 19 – Mar 5Apr 2 – Apr 16
SalemFeb 10 – Feb 24Mar 24 – Apr 7
MerrimackFeb 19 – Mar 5Apr 2 – Apr 16
KeeneMar 5 – Mar 19Apr 16 – Apr 30
DerryFeb 19 – Mar 5Apr 2 – Apr 16
PortsmouthFeb 23 – Mar 9Apr 6 – Apr 20
BedfordFeb 10 – Feb 24Mar 24 – Apr 7
LaconiaFeb 19 – Mar 5Apr 2 – Apr 16
LebanonFeb 28 – Mar 14Apr 11 – Apr 25
WindhamFeb 22 – Mar 8Apr 5 – Apr 19
ClaremontMar 5 – Mar 19Apr 16 – Apr 30
PelhamFeb 22 – Mar 8Apr 5 – Apr 19
SomersworthFeb 19 – Mar 5Apr 2 – Apr 16
LondonderryFeb 10 – Feb 24Mar 24 – Apr 7
DurhamFeb 27 – Mar 13Apr 10 – Apr 24
HamptonFeb 23 – Mar 9Apr 6 – Apr 20
BerlinMar 5 – Mar 19Apr 16 – Apr 30
ExeterFeb 23 – Mar 9Apr 6 – Apr 20

Showing the 24 most populous of 24 New Hampshire cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all New Hampshire cities.

Frequently Asked Questions

When should I plant onions in New Hampshire?

In a typical New Hampshire location, start seeds indoors Feb 22 – Mar 8, then transplant outdoors Apr 5 – Apr 19. Across the state, the outdoor planting window starts as early as Mar 24 in Salem and as late as Apr 16 in Berlin.

When is the last frost in New Hampshire?

The average last spring frost in New Hampshire ranges from April 21 in Salem to May 14 in Berlin, based on NOAA 1991–2020 climate normals.

How long do onions take to grow?

Onions typically take 90–120 days from planting to harvest. Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Other Crops in New Hampshire

When to plant onions in other states

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